1. Field of the Invention
The present invention relates to a method of manufacturing aluminum-substituted hematite to be used as a red pigment for ceramics, lacquer wares, tiles, bricks, roofing tiles, coating materials, and paints.
2. Description of the Related Art
In the past, “Fukiya Bengara” containing iron oxide as a main component, which means refinery red iron oxide, was used as a high-quality red pigment for ceramics. The refinery red iron oxide was manufactured until the middle of the 1960s but is not manufactured today. However, there has been a strong demand for a bright red pigment such as the refinery red iron oxide.
Conventional artificial red iron oxide, which is synthesized by a solid-phase reaction, is directed to high-purity hematite (α-Fe2O3). The high purity hematite synthesized through the solid-phase reaction is stable at temperatures of 650° C. or lower but exhibits a dull color at temperatures of 700° C. or higher. It has been proved that the dull color is attributed to growth of hematite grains. Accordingly, the high-purity hematite cannot be used as a pigment under the conditions that high temperature heating is performed.